A fierce row has broken out over the future of the Sistine Chapel, after one of Italy's most respected writers slammed it as an "unimaginable disaster" where tourists resemble "drunken herds".

Centred on the image of God reaching out to give life to Adam, the chapel ceiling is renowned as Michelangelo's masterpiece and offers a defining image of the Christian faith.

But as the crush of visitors grows year by year, this home to Michelangelo's majestic 16th-century frescoes often feels more like a packed, sweaty, and very noisy railway station.

Five million tourists surge through the chapel every year, craning their necks to get a glimpse of the scenes painted on the 130ft-long ceiling, flouting the ban on flash photography and ignoring pleas from guards to lower their voices.

In an article in Corriere della Sera, Pietro Citati, a leading literary critic and biographer, has demanded that the Vatican limit access to the chapel, claiming it would save the frescoes from damage and restore some decorum to the consecrated site.

Describing a visit, Citati claimed that "in the universal confusion, no one saw anything" and "any form of contemplation was impossible". The answer, he said, was to reduce the number of visitors drastically.

"The church needs money for its various activities, but these monstrous conditions are not possible," said the writer, a close friend of the late novelist Italo Calvino.

The manager of the Vatican museums, which include the chapel, fought back on Friday in the pages of the Holy See's daily paper, L'Osservatore Romano.

"The days when only Russian grand dukes and English lords or [American art expert] Bernard Berenson could gain access to the great masterpieces are definitely over," wrote Antonio Paolucci. "We have entered the era of large-scale tourism, and millions want to enjoy our historical culture," he said. "Limiting numbers is unthinkable."

Michelangelo set to work on the chapel ceiling in 1508 after devising the perfect scaffolding for painting his biblical scenes 20 metres off the ground. The chapel, which also features works by Botticelli, Perugino and Pinturicchio, boasts 300 figures painted across 2,500 square metres and is dominated at one end by The Last Judgment, which Michelangelo filled with nude males reportedly inspired by his visits to Rome's brothels.

Today, the chapel is used during conclaves, when cardinals huddle to select the next pope, and when the pontiff baptises babies there once a year. At all other times, it fills with the 20,000 tourists and pilgrims who form a daily queue that snakes around the Vatican walls.

Paolucci said he had tripled the number of guards to handle the crowds, but last week one guard, who declined to be named, said the chapel was undermanned. "There are two of us against thousands; you'd need 10 guards."

"When it fills up, you can feel the heat rising. We even get pickpockets in here, just like at a street market," he added.

"It's often wall to wall or worse in here," said one tour guide.

Paolucci himself sounded the alarm bell two years ago after restorers gently scrubbed what he described as "unimaginable amounts" of dirt off the frescoes while working at night, after the last tourists had left. The air extraction system designed to suck out the humid breath, sweat, skin flakes, hair, dust and pollution wafting up towards the frescoes was almost 20 years old and urgently needed replacing, he said.

Air conditioning was also needed to reduce the body heat of visitors before they even entered the room, Paolucci said, promising to publish details of plans for a new, sophisticated system in the chapel by year end.

"They should start timed visits," said Cindy Rowlett, a pensioner from Ohio, as she jostled for space. "When they do timed visits at the Met in New York it is more intimate, while this doesn't feel very religious to me."

Paolucci said because the chapel was a place of prayer, timed visits were impossible. "This chapel is a compendium of theology, a catechism in images. Could you limit access to Lourdes?" he wrote. But Citati told the Observer: "Why can't you limit numbers at a holy place if it is at risk? We are condemning it to disaster."

Amid the throng in the chapel, Steve Ferrara, a tourist from Washington DC, said it was the noise that got to him. "This is one of the greatest creations of mankind, if people want to talk they should at least whisper out of respect."

After asking a group of tourists not to sit on the marble steps at the foot of The Last Judgment, the guard watched as his colleague clapped loudly and yelled "silence please" as the hubbub grew.

"Clapping is not exactly elegant," he said, "and after a few minutes people just start talking again."